FIG. 1 is a circuit diagram of a conventional switching regulator (For example, see Japanese Laid-Open Patent Application 2007-4995).
In the example of FIG. 1, constant current control is executed by using operational amplifiers for voltage control and current control, and detection of output current is done by using the voltage difference Vd yielded by the current running in the current sensing resistor.
FIG. 2 is a circuit diagram of a conventional switching regulator that executes constant current output control (For example, see Japanese Published Patent Application 2006-517379).
In the example of FIG. 1, due to using a resistor to detect output current there is a problem of loss arising from the current running in the corresponding resistor. To alleviate such loss there is an approach of reducing the resistance value of the resistor though then there arises the need to use a high precision operational amplifier. In the example of FIG. 2 an integral value is used for current detection thus in a case where the inductor value and the fixed frequency (PWM frequency) are different there arises the need to change the integral constant.